map to queryString

common.java

public static String mapToQueryString(Map<String, String> map) {
        StringBuilder string = new StringBuilder();
        String queryString = map.entrySet()
                .stream()
                .map(Object::toString)
                .collect(joining("&"));
        if(map.size() > 0) {
            string.append("?");
        }
        string.append(queryString);

        return string.toString();
    }